A speed change system for a bicycle comprises a derailleur, and a speed change lever assembly connected to the derailleur through a control cable and mounted to a suitable portion of a frame or handlebar. A speed change operation is performed by operating the speed change lever assembly to actuate the derailleur.
In general, a speed change lever assembly comprises a fixed shaft provided on a frame or handlebar, and an operation lever pivotally supported on the shaft with its base portion connected to a control cable. When the operation lever is pivotally operated in one direction, the control cable is wound in a winding groove of the lever base-portion. On the other hand, when the operation lever is pivotally operated in the opposite direction, the control cable is paid out from the winding groove of the lever under the urging force of a return spring which is incorporated in the derailleur.
A speed change lever assembly such as described above is usually disposed at a position which is remote from a handlebar grip portion, so that the rider must remove one hand from the handlebar to assume a one-hand riding condition at the time of performing a speed change operation. Therefore, in a situation for making an emergency stop or avoiding an abrupt projection or recess of a road while performing a speed change operation, it takes a longer time to move the hand to the braking or steering position, consequently failing to provide a high running safety in such a situation.
To solve the above problem, it has been proposed to mount a speed change lever assembly adjacent to a grip portion of a handlebar for enabling the rider to operate the lever assembly while gripping the handlebar, as disclosed in Japanese Utility Model Publication 62-388785 for example. According to such an arrangement, it is not necessary to remove the hand completely from the grip portion at the time of operating the lever, thus increasing the safety.
As disclosed in the above-mentioned publication, the prior art speed change lever assembly, which is mounted adjacent to the grip portion of the handlebar, comprises a lever shaft fixed to the handlebar by a mounting band or the like, and a speed change lever pivotally mounted on the lever shaft.
However, since a brake lever must be provided inwardly of each grip portion of the handlebar, it is very difficult to make a space for mounting the speed change lever assembly. Further, the speed change lever assembly may interfere with the brake lever assembly, hence making it very inconvenient to operate the speed change lever assembly.
On the other hand, there has been an increasing need in recent years for providing a derailleur even with respect to children bicycles, mini-bicycles and the like. However, the prior art speed change lever assembly described above is designed for application to derailleurs having five or more speed stages. Thus, the prior art speed change lever assembly is complicated in structure to result in an increase of the production cost.
Due to the above problem, it is difficult to apply the prior art speed change lever assembly to bicycles such as children bicycles, mini-bicycles and the like, which have a small number of speed stages.